Method and system for preparing ammonia fertilizer by using nitrogen in air

The invention discloses a method and system for preparing an ammonia fertilizer by using nitrogen in air, and the method comprises the following steps: compressing the air through a compressor, and feeding the compressed air into an air buffer tank after passing through a filter; air in the air buffer tank is alternately fed into a first air separator and a second air separator, and the first air separator and the second air separator are alternately pressurized and decompressed through an air pressure adjusting device; mixing nitrogen with water vapor, and inputting the mixture into the electrolysis chamber; meanwhile, purified water is input into an electrolytic bath; the nitrogen oxide reacts with hydrogen ions in water to generate ammonia gas, and the ammonia gas is input into an ammonia gas recovery tank; the generated oxygen and the unreacted nitrogen are respectively recovered into a second oxygen storage tank and a second nitrogen storage tank; and finally, collecting and treating the generated ammoni